High progesterone levels during early pregnancy are a normal occurrence because progesterone is produced in the placenta, according to the National Women's Health Resource Center. High progesterone levels combined with high estrogen levels decrease ovulation during pregnancy.
During pregnancy, progesterone levels are elevated until the birth of the baby. High progesterone levels promote the growth of milk-producing glands within a woman's breasts during pregnancy, explains the National Women's Health Resource Center. This ultimately prepares the woman for breast feeding once the baby is born. The elevated levels of progesterone often produce symptoms of premenstrual syndrome, such as mood swings, bloating and breast tenderness.
Women who are trying to get pregnant often have progesterone levels checked regularly as part of fertility evaluations. When progesterone levels are elevated, the results typically indicate ovulation has occurred, notes Fertility Authority. When a woman experiences a miscarriage, toxemia, unusual bleeding during pregnancy or a stillbirth, progesterone levels are checked and often reveal lower levels. Obesity, high levels of stress, poor diet, insulin resistance and a lack of exercise often contribute to lower progesterone levels. In rare cases, when progesterone levels are higher than normal, it can indicate ovarian cancer, adrenal cancer or congenital adrenal hyperplasia.